ANS:C - patenting

The heat treatment process typically used for steel wire containing more than 0.25% carbon is "patenting." Patenting is a heat treatment process specifically designed for high-carbon steel wires. It involves heating the wire to a temperature just below its lower critical temperature, then subjecting it to rapid cooling, often by passing it through a lead bath. This process helps in refining the grain structure of the steel, reducing its hardness, and improving its ductility and formability.